Understanding COVID-19 Testing Methods: Molecular, Antigen, Antibody

Updated: Jan 12



Coronavirus cases in the Philippines continue to soar daily even during the lockdown despite the government’s initial measures to contain the outbreak. This serves as an indication that we should take immediate action to double prevention efforts for COVID-19 such as sanitization, disinfection, and most importantly, mass testing, as the death toll gets higher each day.


Why Test?


COVID testing is crucial because it helps the public mitigate the effect of the virus by identifying those who are infected. According to the U.S. Food and Drug Administration (FDA), there are different types of COVID testing methods that are available for usage: molecular test, antigen test, and antibody test.


Molecular Test


Molecular testing, also known as reverse transcriptase polymerase chain reaction (RT-PCR), is a diagnostic test that uses a nasal or throat swab or sometimes the saliva to collect samples of cells and fluids from the respiratory system to detect the genetic material of SARS-CoV-2, the virus that causes COVID-19, using a laboratory technique called polymerase chain reaction.


How is the procedure done?

  • A doctor or health care professional inserts a 6-inch long nasal swab (like a long Q-tip) into the cavity between the nose and mouth (nasopharyngeal swab) for 15 seconds and rotates it several times. This may somewhat be uncomfortable since the body is not used to having an object inserted in that area. It may activate the lacrimal reflex (discharge of tears) and may trigger a gag reflex since the swab will touch the back of the throat

  • The process is then repeated on the other side of the nose to make sure enough material is collected for the test.

  • The sample gets sealed in a tube and sent to a lab for analysis

  • Although it’s not considered the best way to get a good sample, a saliva test may be done if discomfort is an issue with a nose or throat swab. You spit into a tube several times to provide a sample of your saliva for testing. The tube is sealed before being sent to a lab for analysis

CDC notes that proper collection of specimens is the most important step in the laboratory diagnosis of infectious diseases. A specimen that is not collected correctly may lead to false-negative test results.


How accurate is this test? Is another test needed for validation?


Molecular tests help identify a person with an active coronavirus infection and they are more widely used because they are highly accurate. If performed correctly by healthcare experts, the swab results can come close to a 100% accuracy which means another test doesn’t need to be repeated. You may also get your results on the same day (for some locations) or within a week.


Antigen Test


An antigen test, also known as rapid diagnostic test (RDT), detects viral proteins called antigens present in the COVID-19 virus. These antigens are foreign substances capable of stimulating an immune response.


How is the procedure done?


This type of test also uses nasal or throat swabs to get a fluid sample and can produce results in just an hour or less. The World Health Organization (WHO) states that if the target antigen is present in sufficient concentrations in the sample, it will bind to specific antibodies fixed to a paper strip enclosed in a plastic casing and generate a visually detectable signal, typically within 30 minutes. The antigen(s) detected are expressed only when the virus is actively replicating therefore such tests are best used to identify currently infected people.


How accurate is this test? Is another test needed for validation?


Antigen testing is considered practical in most cases because positive results have a high accuracy rate. However, depending on the situation, a doctor may recommend a RT-PCR test to confirm negative results because it’s possible to be infected with the virus but have false-negative results.


Antibody Test


An antibody test, also an RDT, checks your blood for the presence of antibodies or immunoglobulins which are the protective proteins produced by the immune system in response to the presence of a specific virus or in today’s case, COVID-19.


This is used to detect if you had a past infection of COVID-19 or if you are an asymptomatic carrier which means you are infected but you don’t show any symptoms. Although antibodies can help fight infections and provide immunity to the said virus, there is still not enough evidence up to date on how much protection the antibodies provide, how long it may last or whether having a history of COVID would prevent you from getting infected again.


How is the procedure done?


Also known as serology testing, the antibody test is done by a medical professional by finger pricking or drawing blood from a vein in your arm to get a sample for examination.


It looks for two types of antibodies to SARS-CoV-2:

  • IgM antibodies, which happen in early infection

  • IgG antibodies, which are more likely to show up later


Quality rests in Sensitivity and Specificity


The specificity of the antibody test is important for avoiding “false positives” while the sensitivity is important for avoiding “false negatives,” in which the patient’s blood appears free of antibodies against SARS-CoV-2 despite having previously been infected with it. There is a window period between virus infection and the production of IgM and IgG antibodies. So early on during infection, when we want to use rapid antibody tests for diagnosing COVID-19, we need a highly sensitive test. ISPS RDT’s IgM and IgG combined sensitivity and specificity is 90.6% and 99.2%, respectively with a total accordance rate of 95.3%.


How accurate is this test? Is another test needed for validation?


Timing and the type of antibodies may affect result accuracy. It can take 1-3 weeks for your body to make enough antibodies to be detected in a test following your infection and these may stay in your blood even after recovery. Given that timeframe, the test may not show if you are currently infected with COVID-19. Having said this, a second antibody test or molecular test may be needed for a more accurate result.


This alternative testing method may be considered as a molecular or antigen test. It makes use of a mucus sample obtained from the nose or throat that may be analyzed in a doctor’s office or clinic where the sample is collected. Results may be available in minutes.


The FDA informs the public of the purchase and administration of approved COVID-19 Rapid Antibody Test Kits. The product must be acquired through a prescription from a licensed physician from licensed hospitals or drug stores/pharmacies/botica. Online sale is also prohibited. Administration of the test must be performed by a doctor or a trained health professional and interpretation of the results must be guided by a physician.


Conclusion



COVID testing plays an important role in reducing the spread of COVID-19 along with common disinfection processes like misting and bio-fogging. All of these are part and parcel of the new normal for different companies, businesses, and industries.


As the Philippines’ #1 partner in health and safety, ISPS continues to boost mass testing efforts in the country to help flatten the curve. We are offering customizable on-site and off-site COVID-19 testing services as well as COVID-19 test packages like Livzon and Innovita. All results from COVID-19 testing comes with a certification after completion of the test.


Get yourself, your family, friends, co-workers, staff or employees tested with our Rapid Antibody Testing Services or avail our Rapid Testing Kits!


Contact us today or visit our Facebook for more information:

Phone: 0917 861 3850

Email: info@internationalsps.com

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